Control-released urea improved agricultural production efficiency and reduced the ecological and environmental impact in rice-wheat rotation system: A life-cycle perspective

Abstract

Application of control-released urea (CRU) is considered as an attractive means to improve nitrogen use efficiency (NUE) while maintaining and even improving the grain yield. However, life-cycle impacts, including economic benefit, energy flow, and environmental and ecological benefits, from CRU production to crop harvesting at various application strategies remain unclear. To fully assess the life-cycle impacts of CRU application, a 2-year field experiment covering an area of 3.78 ha was conducted in Yangtze River Delta, China during 2019−2020 with a rice-wheat rotation. The grain yield, NUE, net profits, energy flow, life-cycle N and C footprints, ecosystem economic benefits from the application of bulk blending urea (BBU) consisting of CRU and farmer’s conventional urea were evaluated and compared to farmer’s conventional urea fertilizing practice. Results suggested that twice-split fertilization of BBU improved the total grain yield and NUE, while single-dose fertilization of BBU had no impacts on total grain yield but reduced the NUE. By optimizing fertilization rate and frequency, the total net profit was improved from 3016 $ ha −1 to 3300 $ ha −1 across the rice-wheat-rice season from 2019 to 2020. Compared to the farmer’s conventional urea fertilizing practice, application of BBU not only significantly decreased the life-cycle reactive N (Nr) losses and greenhouse gas (GHG) emissions by 35.6%−54.5% and 34.1%−44.7% respectively, but also reduced the N and C footprints by 41.1%−60.8%, and 41.8%−42.3% respectively, which was mainly profited by decreasing the on-farm emissions of CH 4 , N 2 O, NH 3 , and NO 3 − . The ecosystem economic benefits were improved by 18.1%−59.8% because of the reductions in labor, ecosystem, and human health costs. Energy productivities also were enhanced by 3.9%−12.4% except for single-dose fertilization of BBU at the rate of 300 kg N ha −1 . Comprehensive analysis indicated that twice-split application of BBU at the rate of 300 kg N ha −1 obtained relatively high performances for grain yield, net profit, energy productivity, reductions in N and C footprints, and ecosystem economic benefit, which demonstrated that twice-split application of BBU was an effective fertilization strategy to balance the economic benefit and ecological and environmental impacts in the rice-wheat rotation system, thereby promoting agricultural sustainability. • LCA and energy flow analysis revealed the life-cycle N, C, and energy footprints in a rice-wheat rotation system. • DNDC model simulated the reductions of Nr losses and GHG emissions by application of BBU. • Appropriate BBU fertilization increased the grain yield and net profits. • CRU was more sustainable than conventional urea from the life-cycle perspective.